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IntroductionBrno Valley Dam on the Svratka River (56.19 km) was put into operation in 1940 to decrease the damage caused by river flow during floods, to supply water to the city of Brno, and to control the flow under the dam. The area of the water reservoir is 259 ha with a total volume of 17.7 million m 3 . The banks of the reservoir in the Osada area are continuously damaged to an approximate length of 250 m, where the slope-to-vertical abrasion caverns reach heights of up to 5 m (detailed localization GPS: the banks from 49°14'44.063"N, 16°30'22.781"E to 49°14'45.298"N, 16°30'11.502"E).Pol. J. Environ. Stud. Vol. 27, No. 2 (2018), 793-799 AbstractThe Osada Recreation Area on the left bank of Brno Valley Dam (Czech Republic) represents a location that is extremely affected by the abrasion process due to a combination of adverse factors (fetch related to the dominant wind speed and direction over the water surface causing wave motion, the geological structure and morphology of banks, boat traffic). Our research focused on confirming the hypothesis that properly designed low-cost biotechnical structures can contribute to the active stabilization of a bank under special protection status. The hypothesis was verified by the method of wave train analysis (to prove wave height reduction) and spectral analysis (to prove wave energy dissipation due to breaking) of synchronized data collection of wave motion. The records of water surface motion were taken with the aid of electronic devices on the windward and leeward sides of the structure specifically assembled for the purposes of our research. Comparing the results of both sensors proved the effect of the stabilizing structure (double willow wattling) consisting in wave height and peak spectral energy density reduction. The leeward values decreased to approximately half the windward values due to the process of waves passing through the structure and energy dissipation.

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This contribution deals with use of elements of cooperation and competition in teaching at secondary schools as perceived by secondary school teachers. For the research quantitative questionnaire survey is used. The objective of the research is to find out whether secondary school teachers use elements of cooperation and competition in their teaching, eventually up to what extent, then which advantages and disadvantages of these methods they find. Research sample consists of 108 respondents—secondary school teachers. Obtained data were evaluated using descriptive statistics and then interpreted. From the obtained results recommendations for teaching practice in the field of secondary school education are provided in the final part of the contribution.

The article deals with issue of water reservoir banks stability in places where the abrasion is developed, and possibility of using active anti -abrasive protection that is designed from natural materials. The issue of banks stability is demonstrated on the example of the reservoir dam Brno particularly in the Osada area. In this part of reservoir shoved the most developed bank abrasion as high abrasion caverns and abrasion platform. This natural structures are home of kingfisher (Alcedo attis, L.) who nests on this headwalls. As a result, there is a conflict of interests -the banks are subject to special protection statute under which the banks are not allowed to alter. From this mason is very suitable use active anti -abrasive protection of banks.